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Eternal Rye – Improving Plant Breeding Methods to Meet the Demands of a Growing Population

byZEISS Microscopy 25 January 2024 3 min read

Introduction

No rubber boots, no wholewheat bread, no straw hat. In his office at Martin Luther University in Halle, Germany, Dr. Steven Dreissig welcomes us to his desk in a relaxed polo shirt and jeans. Since 2019, Dreissig has been working with a team at the Institute of Agricultural and Food Sciences to research how environmental influences change the DNA of rye. In doing so, he is following in the footsteps of several generations of scientists. Breeding research is used to improve plant breeding methods and develop climate-resistant varieties to support future food security.

Why Rye?

Rye is extremely hardy. It has good cold tolerance, is disease resistant and is not very demanding. Rye is cultivated worldwide, right up to the Arctic Circle and at up to 4,000 m above sea level. It can grow in sandy soils with low fertility and needs less fertilizer than other temperate cereals.

Humanity started to cultivate rye about 5,000 years ago. Today, plant researchers are particularly interested in the “unstructured” reproductive behavior of rye, which they want to transfer to other “inbreeding” grains to improve hybrid breeding.

Eternal Rye | Martin Luther University Halle

Eternal Rye Cultivation

The research of the Plant Reproductive Genetics Group around Dr. Dreissig focuses on the impact of genetic and environmental factors on the sexual reproduction of plants in general. In a special project on “Eternal Rye Cultivation”, the group endeavors to understand the genomic factors that are responsible for the size and morphology of rye’s pollen and therefore its reproduction behavior.

The long-term field trial at Halle was already started in 1878 when the agronomist Julius Kühn planted a trial field of winter rye (Secale cereale L.) that encompassed six plots of 1,000 m². It is the second-oldest permanent experiment in the world. Only in Rothamsted, England – at the largest and world’s oldest agricultural research institute – a comparable series of experiments began 35 years earlier.

In order to understand the mechanisms that influence the crossbreeding behavior of rye, the group investigates the plant’s flowering and fertilization behavior as well as the factors influencing pollen size and distribution. Once the responsible genome is found and the mechanism behind pollen size is understood, the next step would be a targeted transfer to other crops.

Ultimately, we will consider how answers to these questions can be transferred into the overall development of improved breeding methods.

Steven Dreissig | Martin Luther University Halle, Germany

Pollen is Key

Rye flowers from April to early September and pollinates freely. Being self-incompatible and unable to fertilize itself, it depends on neighboring plants for pollen. Therefore, the plant sheds a lot of pollen to increase its chance of fertilization.

The optimal size of pollen is a compromise between flight distance and the ability to hit and stick to surfaces. The smaller and lighter the pollen, the more it integrates into the airflow and tends to flow around objects. The larger the pollen, the greater its ability to settle on surfaces and the more energy can be given to the pollen to grow through the pistil.

Improving Breeding Methods with Light Microscopy

To investigate the pollen, the anthers are removed from the flowering plant under a stereo microscope. The pollen is then analyzed and counted, either with fluorescence microscopy or flow cytometry, which provides information on the vitality and size of the rye pollen. This evaluation is based on hundreds of plants to be able to draw conclusions on how fertility is influenced by environmental conditions and how the average pollen size is related to the genome sequence.

Anthers, Eternal Rye, acquired with ZEISS Stemi 508 — Copyright: Martin-Luther-University Halle-Wittenberg, Germany

The six anthers are manipulated out of the flowering plant. Image aquired with the ZEISS Stemi 508 stereo microscope.

Pollen, Eternal Rye, acquired with ZEISS Axio Observer — Copyright: Martin-Luther-University Halle-Wittenberg, Germany

Pollen grains normally contain three nuclei. Image aquired with the ZEISS Axio Observer light microscope.

Addressing Global Hunger

Knowing the genes responsible for the pollen size and formation enables the targeted transfer to other crops, therefore facilitating the development of correspondingly fertile, high-yielding varieties.

This approach not only promises to increase food production but also contributes to sustainable agriculture, ensuring that we can nourish the present without compromising the ability of future generations to meet their nutritional needs. With continuous research and development, scientists can harness the full potential of rye and other crops that can feed the world.

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